Mechanical coupler



FIG. 1 is a front elevation view of another embodiment of a coupler design of the present invention, which is substantially identical to the rear elevation view of the coupler;

FIG. 2 is a top plan view of the coupler of FIG. 1;

FIG. 3 is a bottom plan view of the coupler of FIG. 1; and,

FIG. 4 is a left side elevation view of the coupler of FIG. 1, which is substantially identical to the right side elevation view of the coupler of FIG. 1. 

The ornamental design for a mechanical coupler, as shown and described. 